Liquid storage tanks, e.g., gasoline storage tanks, are commonly employed to store gasoline in open tanks having floating roofs resting on the liquid level, moving up and down as the liquid level changes. In order to measure the amount of liquid in each tank and to access its quality gauge wells have been used. Each gauge well is a pipe extending from above the floating roof to adjacent the bottom of the tank. A float is positioned inside the gauge well pipe to move up and down with the level of liquid stock, and periodically to take a sample of the stock for analysis. One of the problems with floats in the prior art has been that petroleum vapors escaped out the top of the gauge well pipe causing complaints about the pollution of the atmosphere. Furthermore, when samples were taken it was necessary to remove the float and replace it with a sample container. It was also found that taking samples was not reliable because the stock in the confined space in the gauge well would not be representative of the stock generally in the tank. Accordingly, the gauge well pipe was pierced by slots spaced up and down the length of the gauge well pipe. Burrs left from cutting the slots frequently fouled the float and hung the float on a burr thereby preventing it from its purpose and sometimes the cable or tape broke, allowing the sampler container to fall to the bottom of the pipe with no chance of ready retrieval. Typical of patents relating to such a system is U.S. Pat. No. 4,468,975 to Sayles. Also, the float of Sayles apparently was chosen such that the outside diameter of the float approximated closely the inside diameter of the gauge well pipe which caused problems of using same in a retrofitted pipe system.
It is an object of this invention to provide an improved system wherein the float and sample container are the same article. A further object is to provide a float which accomplishes the sealing function with little chance of becoming lodged on a burr or the like in the well pipe. It is another object of this invention to provide an improved system whereby a sample container may be retrieved if accidentally dropped in the gauge well pipe. Still other objects will become apparent from the more detailed description which follows.